After infection with oncoviruses, the risk of developing certain forms of cancer increases. Such cancer-causing viruses are the cause of disease in about 10% to 20% of all cancers. Many oncoviruses are well known and well described to science.
What are oncoviruses?
Viruses are infectious particles that reproduce and are subject to the rules of evolution. However, they are not true living organisms in the classical sense, since they do not have their own metabolic apparatus but rely on that of host cells. In the process, they introduce new genetic material into the host cell’s genetic material or modify the host cell’s genetic material. Such processes sometimes lead to the transformation of benign cells into tumor cells. The viruses that have been shown to cause cancer in multicellular animals and in humans are oncoviruses. Many different mechanisms play a role in the development of cancer, depending on the type of virus. Some viruses activate cancer-causing genes that are already present in the host cell. Other viruses incorporate viral oncogenes into the host cell. There are oncoviruses among all groups of viruses, i.e., among retroviruses as well as DNA viruses.
Occurrence, distribution, and characteristics
Hepatitis viruses are the most relevant oncoviruses for humans. Hepatitis B viruses and hepatitis C viruses dramatically increase the likelihood of developing liver cancer in certain courses of infection. Hepatitis C and hepatitis B are transmitted through blood transfusions, sexual intercourse, and directly at birth. However, there are also many hepatitis infections that originated in an unclear way, perhaps from the smallest skin lesions. If the infection is chronic, i.e. if the immune system does not eliminate the viruses from the organism, hepatocellular carcinoma may develop. Through biochemical detection of antibodies and antigens, laboratory analysis allows accurate diagnosis of hepatitis B and hepatitis C, as well as the current infection status. Patients themselves, on the other hand, often do not notice creeping chronic hepatitis. This is why laboratory tests to detect hepatitis antigens and hepatitis antibodies are part of routine medical check-ups. Those who have not yet had contact with hepatitis B viruses can be vaccinated. Hepatitis B vaccination prevents infection with this virus and thus also contributes to general cancer prevention. Human papillomaviruses (HPV) are also responsible for a large proportion of cancers caused by viruses. The most important target organ of this virus is the cervix. Papillomaviruses are those viruses that make sexual intercourse a cancer risk because transmission occurs between the genitals or during oral sex. Cervical cancer is one of the most common cancers in women. In addition to cervical cancer, HPV viruses also cause penile cancer or oral cancer in rare cases. Since 2006, there is an approved vaccine against certain HPV viruses. HPV vaccination is thus another vaccine that can be used for cancer prophylaxis. The HTLV-1 virus is a retrovirus that sometimes causes leukemia, or blood cancer, in humans. As a retrovirus, it belongs to a similar group of viruses as the HI viruses. As with HIV, infection is permanent. However, HTLV-1 infections are rare and even more rarely result in T-cell leukemia. Epstein-Barr virus is a herpes virus. Epstein-Barr viruses cause glandular fever. The viruses are mostly harmless and infect almost 100% of all people. The host cells of these viruses are the B lymphocytes in the immune system. Epstein-Barr viruses probably play a role in a rare but very severe form of lymphoma, Hodgkin’s disease. However, how exactly this form of cancer develops, why most people survive infection with Epstein-Barr virus without consequences, and why the cancer nevertheless develops only in very rare cases are questions of current research.
Diseases and medical conditions
Viruses are a constant threat to the organism. Many routes of infection and modes of development of cancer are known. But many cancer-causing mechanisms and the role that viruses play in them have not even been described. Many viruses, such as the hepatitis viruses and the herpes viruses, are not extremely infectious. However, once people become infected with them, they often struggle with long-term effects of these viruses, including the development of cancer. With hepatitis viruses, many routes of infection are not entirely clear.Sexual intercourse is a particularly intense physical contact that can also lead to infection by viruses that are otherwise very difficult to transmit. Condoms reduce the risk of viral infections during sexual intercourse. Many cancers have multiple causes. Alcohol damages the liver and very quickly leads to liver destruction and liver cancer in hepatitis B patients. Tobacco smoke damages the mucous membranes around the mouth and, together with HPV viruses, can promote oral cancer. Therefore, in addition to avoiding viral infections, avoiding other carcinogens is important for overall prophylaxis. Regular visits to the doctor lead to a good diagnostic overview of what is going on in one’s body.
